1. Field of the Invention
The present invention relates to a vibrating mirror element, and more particularly, it relates to a vibrating mirror element comprising a movable portion vibrating with a piezoelectric film.
2. Description of the Background Art
A vibrating mirror element comprising a movable portion vibrating with a piezoelectric film is known in general, as disclosed in Japanese Patent Laying-Open No. 7-181414, Japanese Patent No. 3561544 and Japanese Patent Laying-Open Nos. 2007-271788 and 10-242795.
The aforementioned Japanese Patent Laying-Open No. 7-181414 discloses an optical scanner comprising a mirror portion provided with a mirror, a vibration input portion mounted with a piezoelectric element, a plate made of metal integrally formed with an elastic deformation portion provided between the mirror portion and the vibration input portion and a piezoelectric element mounted on the vibration input portion. This optical scanner is so formed that the elastic deformation portion is vibrated by inputting vibration equal to a resonance frequency from the piezoelectric element into the plate, to vibrate the mirror portion provided with the mirror. The optical scanner described in the aforementioned Japanese Patent Laying-Open No. 7-181414 is so formed that the mirror portion is supported in a cantilever manner by the elastic deformation portion and the vibration input portion and the mirror portion corresponding to a forward end portion of this cantilever is vibrated, to scan an object with light reflected from the mirror.
The aforementioned Japanese Patent No. 3561544 discloses a mirror element comprising a substrate, a flat plate shaped piezoelectric element in which a piezoelectric film is held between an upper electrode and a lower electrode, a mirror layer formed on a surface of the piezoelectric element and a support portion provided on the substrate and supporting a first end of the piezoelectric element from a lower portion. A connecting terminal is formed in the support portion formed on the substrate of the mirror element. The lower electrode and the connecting terminal of the piezoelectric element are electrically connected to each other through a conduit formed in the support portion. The aforementioned Japanese Patent No. 3561544 does not describe a material of the substrate of the mirror element.
The aforementioned Japanese Patent Laying-Open No. 2007-271788 discloses a vibrating element comprising a silicon substrate integrally formed with torsion beams swingably supporting a mirror portion arranged on a center and both ends of the mirror portion, a base mounted with the silicon substrate and four piezoelectric elements for swinging the mirror portion. Each torsion beam of the vibrating element has a first end supporting an end of the mirror portion and longitudinally two-forked second ends coupled with a frame portion of the silicon substrate. The piezoelectric elements are arranged on the two-forked portions of the torsion beam (vicinity of the second ends) respectively. The vibrating element described in the aforementioned Japanese Patent Laying-Open No. 2007-271788 is so formed that the four piezoelectric elements in total are provided in the vicinity of the two-forked second ends of a pair of the torsion beams supporting the both ends of the mirror portion and the mirror portion is swung by switching excitation to these piezoelectric elements. Each piezoelectric element has a structure in which a piezoelectric layer is held between an upper electrode and a lower electrode.
The aforementioned Japanese Patent Laying-Open No. 10-242795 discloses a cantilever-shaped piezoelectric element comprising a piezoelectric substrate having upper and lower surfaces formed with metal electrodes and titanium electrodes respectively and a silicon substrate having a holding portion of the piezoelectric substrate. This piezoelectric element is formed with a groove on a side of the lower surface of the piezoelectric substrate. The metal electrode and the titanium electrode formed on the side of the lower surface of the piezoelectric substrate are extracted to outside of the piezoelectric element by forming an extraction portion in the groove of the piezoelectric substrate.
However, the optical scanner described in the aforementioned Japanese Patent Laying-Open No. 7-181414 has a structure in which the mirror portion is supported in the cantilever manner and vibrated, and hence stress is concentrated on the elastic deformation portion supporting on the mirror portion corresponding to the end of the cantilever, thereby easily causing fatigue breakdown. Thus, reliability during long drive is disadvantageously reduced.
In the mirror element described in the aforementioned Japanese Patent No. 3561544, the lower electrode holding the piezoelectric film is electrically connected, and hence the connecting terminal and the conduit must be formed in the support portion supporting the piezoelectric element. Thus, a structure for electrically connecting the lower electrode and outside is disadvantageously complicated.
In the vibrating element described in the aforementioned Japanese Patent Laying-Open No. 2007-271788, the piezoelectric elements are arranged on the respective second ends of the torsion beams employed as the partial silicon substrate, and hence a wiring pattern and the like for electrically connecting not only the upper electrodes of the respective piezoelectric elements but also the lower electrodes must be formed. Thus, a structure for electrically connecting the lower electrodes and outside is disadvantageously complicated.
In the piezoelectric element described in the aforementioned Japanese Patent Laying-Open No. 10-242795, the groove for extracting the electrode on the side of the lower surface is formed on the piezoelectric substrate and the extracting portion of the metal electrode and the titanium electrode must be formed in the groove of the piezoelectric substrate. Thus, a structure for electrically connecting the electrodes on the side of the lower surface and outside is disadvantageously complicated.